Field of the Invention
This invention relates to a brake system having a hydraulic booster type braking hydraulic pressure generator and more particularly to a hydraulic booster which is arranged to ensure the brake system to be adequately fail-safe when one of two hydraulic pressure channels of the booster fails to operate.
Another aspect of the present invention relates to an automatic control system and more particularly to a system in which an antiskid control device is combined into one unified body with a hydraulic booster.
The conventional hydraulic boosters used for the brake systems of vehicles include the kind having two independently arranged braking hydraulic pressure channels. One of the two channels is arranged to be of the hydraulic booster type and the other to be of the ordinary master cylinder type. An example of this kind has been disclosed, for example, in U.S. Pat. No. 4,482,192.
It would be advantageous for the hydraulic booster of this kind to be arranged such that, in the event of an abnormality such as a failure of one of the two channels, the booster is capable of ensuring a sufficient braking force for the whole vehicle in that event and also capable of saving the vehicle operator from falling into a panicked state due to any abnormal brake pedal operating feeling that arises on the occasion of such an abnormality.
Meanwhile component devices of varied kinds have been proposed for use in the brake system of a vehicle, including a hydraulic booster for boosting a braking force, an antiskid control device for preventing a locked state of wheels from occurring during brake application, etc. Generally, these devices are individually arranged.
However, since they are to be used as components of one and the same brake system for a vehicle, appropriate combination of them into one unified body would advantageously facilitate assembly and mounting work on the vehicle, simplify the structural arrangement and enhance the performance of the system.
In combining a hydraulic booster and an antiskid control device into one unified body, however, it is conceivable, for increased safety of the braking hydraulic pressure system of a vehicle, to arrange the system to have two channels, one arranged to be operated by a hydraulic booster and the other to be normally operated with hydraulic pressure generated by a pushing force of a piston, and to utilize the hydraulic pressure obtained from a pressure accumulator of the hydraulic booster in accomplishing antiskid control over the latter channel which is normally operated. With the system arranged in this manner, however, if one of the two channels should come to fail to adequately operate, the other would be affected thereby.
This invention is aimed to attain the above-stated advantage. It is therefore an object of this invention to provide a hydraulic booster type braking hydraulic pressure generating device which has two independent braking hydraulic pressure channels and is capable of channels when the other comes to fail to operate.
It is another object of this invention to provide a hydraulic booster type braking hydraulic pressure generating device which is capable of preventing any abnormal increase in the pedalling stroke of the brake pedal even in case that one of braking hydraulic pressure channels comes to fail.
It is further another object of this invention to provide a brake system for a vehicle having a hydraulic booster and an antiskid control device combined into one unified body.
It is further another object of this invention to reduce the size of the whole system by virtue of the above-stated combination into one unified body.
It is a stated further another object of this invention to provide a brake system for a vehicle which is capable of retaining at least a given amount of a vehicle braking force on a vehicle even in the event of a failure of one channel of the brake system.